Abstract: " Aggression in youth ice hockey is prevalent and has many negative consequences including the possibility of injury (Widmeyer & McGuire, 1993). Multiple antecedents lead to aggression (Bushman & Anderson, 2001), however, emotions and related cognitions are often the precursor. Very few attempts have been made to control aggressive behavior in sport. Therefore, the Playing Tough and Clean Hockey Program is a nine session program created to teach youth ice hockey players emotional management skills to reduce aggressive behavior while continuing to play physical hockey. Four youth ice hockey players participated in a season long (30 or more games per participant) single-subject multiple baseline AB (baseline, program) design study. The study had two purposes, (1) examine the program's influence on the emotional control, emotional toughness, and aggressive behavior of participants, and, (2) to conduct an evaluation of the program's effectiveness. It was hypothesized that participants would have enhanced emotional control and toughness (i.e., ability to respond positively in an adverse situation) and would exhibit fewer acts of aggression following the program's implementation. Participants completed post-game reports after every game assessing their performance, emotions, aggressive feelings, emotion management, and emotional control skills success. Games were videotaped throughout the season to record instances of aggressive and retaliatory behaviors. Results revealed that participants perceived the program enhanced their ability to maintain emotional control and toughness, and play tough and clean hockey. Correlations revealed that across the four participants' perceptions of emotional control and toughness were often positively associated with tough and clean hockey and negatively associated with perceptions of aggressive hockey. Analysis of on-ice aggressive acts showed that each participant was less aggressive in the program phase, but effect sizes varied with the greatest effects being found with the most aggressive player. Moreover, participants reduced the percentage of time they retaliated to being provoked. Participants felt the program was effective, thus suggesting it as method for teaching emotion management skills to youth hockey players to reduce aggression. Practical implications and future directions were forwarded, especially the need for sport psychology to view aggression as a more complex construct. "--Abstract from author supplied metadata.